Echocardiography is an ultrasound-based imaging technique which can be performed through the esophagus (which lies behind the heart) and through the chest wall; both TEE and TTE are performed routinely as a monitoring and diagnostic tool at different times in the course of one cardiac surgery. The purpose of the study is to compare these two methods of echocardiography and comparing them to the 2D TEE and TTE assessments, which are routinely performed simultaneously. The study will also compare the echocardiography data to a third technique, thermodilution, which measures cardiac function via a pulmonary artery catheter.